Análise comparativa do dimensionamento de galerias de águas pluviais: abordagem na condição de escoamento permanente e uniforme e na condição de escoamento não permanente e não uniforme

Abstract

The urban microdrainage system is responsible for capturing rainwater and directing it to the macrodrainage system, and must be designed to provide safety and comfort to the population in relation to the flow of rainwater. One of the constituent parts of this system is the rainwater gallery that can be dimensioned based on the condition of permanent and uniform flow, through the Rational Method for example, and based on the non-permanent and non-uniform flow with the Saint-Venant Equations. Although this last condition is theoretically more precise and easily accessible, designs based on the Rational Method are frequently used in Brazil. In this way, it is intended to compare the hydraulic-hydrological conditions and effects, the diameters of the galleries, the water depth, the flows and flow velocities obtained in each consideration. For this, the design of the two conditions was carried out in the Parque do Espraiado subdivision in the municipality of São Carlos/SP, using the SWMM software for the numerical resolution of the Saint-Venant Equations. The design conditions adopted were speed less than 5m/s, Froude number less than 1, minimum diameter of 500mm and water depth less than or equal to 0.80. The results indicated that the flows obtained by the Rational Method were lower than those found in the SWMM software, with a difference of 9.09% in the final flow. In addition, the velocities in the two methods differ on average by 12.75%, with the highest values ​​obtained by the Rational Method, unlike the water depth, which in the consideration of non-permanent and non-uniform flow presents the highest values. It was found that the design performed by the Rational Method would not meet all the design conditions in an analysis in the condition of non-permanent and non-uniform flow, resulting in exchanges for larger diameters in 15 of the 32 gallery sections in the enterprise.